The use of rotational plate cathodes is described in U.S. Pat. No. 1,073,868. The desired metal, here, precipitates onto the cathodes in the shape of a plate-like coating.
There has not been much practical use of rotational electrodes stationary plate cathodes being mainly in use to day.
The advantage of stationary plate cathodes lies in the simplicity of operation and relatively low maintenance costs. They are, however, quite dependent on manual handling in the tankhouse.
The first rotational cathodes, like the stationary plate cathodes, produced platelike cathodic deposits. The only difference was the geometry of the cathodes. The first mentioned were circular and the last mentioned rectangular. One of the reasons why rotational plate cathodes were not widely accepted may be the difficulties experienced in stripping the deposited metal from the cathodic material.
Development of the art of chemical processes during later years led to complete automation of all unit operations in an integrated process. In the case of electrolysis with stationary plate cathodes, partial automation is achieved by use of computors. The computors keep track of retention times of the cathodes in the electrolyte, and when the expected amount of metal is deposited, the computer will send an overhead crane to pick up the cathodes and move them to the stripping section. Then, the crane returns with a fresh mother plate cathode to the vacant place in the electrolytic tank.
Practical operation of such an automated electrolytic process is very complicated and many producers, thus, maintain old routines with manual labour operation.
In order to fully automate an electrolytic process, the concept of electrolysis must be changed to a new method maintaining the same metal quality as that obtained by the old methods, at the same costs, but permitting automation.